This invention relates to the generation of ozone for various industrial applications and in particular to an improved corona discharge type of ozone generator capable of providing high ozone output while using lower voltage input as compared to conventional generators and with significantly lower energy consumption.
Ozone O.sub.3 is a blue gas consisting of three oxygen atoms and having a characteristic, pungent odor. Ozone is formed when ordinary molecular oxygen is subjected to electrostatic discharge. Ozone has a density 1.5 times that of oxygen and is explosive by percussion or under variations of pressure.
Ozone is used as a bleaching agent, as an oxidizing agent and commonly as a disinfectant for air and water solutions. Odor- and taste-producing hydrocarbons can be effectively eliminated by ozone oxidation. Iron and manganese compounds which discolor water are diminished by introduction of ozone. Ozone presents several advantages over chlorine for bacterial and viral disinfection of water. Ozone is up to 5000 times more rapid in its action than chlorine, and after ozone treatment there is not the undesirable taste and odor which is associated with chlorine treatment. Also, chlorine treatment can introduce various chlorine compounds to water such as chloroform and trihalomethane compounds which are potentially carcinogenic.
Corona discharge devices for production of ozone have been in use for sometime. The principle forms of corona discharge devices include solid plate-type generators and tube discharge type generators. Ozone generators are constructed in the general form of a "sandwich" consisting of a conductor layer--dielectric layer--conductor layer with the conductors being solid metallic plates. This sandwich may then be used as a flat unit which is commonly referred to as a "plate-type" ozone generator, or alternatively, the opposing edges of the sandwich may be brought into contact to form a cylinder of the sandwich. The cylinder form is referred to as a tube-type generator.
Temperature control is a critical aspect of ozone production. The temperature of the dielectric elements at the site of corona formation must be controlled as ozone output will vary as a function of generator temperature. In addition, excessive temperatures will affect the dielectric material itself causing changes in the thermal characteristics of the dielectric material and possible breakage of the dielectric.
As a result of the need for temperature control, tube-type generators are the most common generator style as they can provide higher ozone production rates due in large part to the ability to configure a water jacket about the electrical discharge area to provide cooling of the unit. Heretofore, air-cooled ozone generators have presented the disadvantage of poor temperature control. Since the critical temperatures for ozone generator dielectrics are in the range of 120.degree. F. to 130.degree. F., it is difficult to balance sufficient air flow through the generator for cooling with the lower air flow needed to permit the O.sub.2 to O.sub.3 reaction to occur. The one option for dealing with this problem is to utilize refrigerated air to cool the generator. However, once the expense of air-cooling equipment is included the initial lower air-cooled system cost is in the range of water cooled systems. Therefore, the commonly used method of ozone generator cooling is water or chilled water, contained in a water jacket, which surrounds a tube-type corona discharge portion of the generator.
It will be appreciated that this use of water to cool the ozone generator adds substantially to unit cost and unit operation cost. Also the use of water flow cooling requires the availability of a water source and reduces the portability of the generator. At best, if portability is desired, water cooling requires the addition of a self-contained water circulation and water refrigeration system which adds substantially to the cost of the device. These mobility limitations of water cooled devices limit their utility to fixed location applications such as water system purification.
As ozone increasingly becomes the method of choice for deodorizing motel and hotel rooms and used automobiles and private homes, the burden of water cooling cost and lack of mobility presents a substantial limitation on the application of ozone for these purposes. This problem is further compounded by in ability of previous air-cooled ozone generators to provide sufficient ozone production to accomplish these deodorizing tasks in a reasonable amount of time.
Another limitation of prior ozone generators of all types is that they require the application of very high voltages. Voltages on the order of 5,000 to 25,000 volts are commonly used in present ozone generators with power consumption ranging from 3.5 amps to produce 0.84 lbs O.sub.3 per day to 5 amps to produce 2.0 lbs O.sub.3 per day. This, respectively, represents 0.24 lbs/amp and 0.28 lbs/amp.
The present invention provides a portable ozone generator which avoids the need to water cool the generator and while solving the problems of inefficient air-cooling and low O.sub.3 production per unit of power consumption and ozone deterioration of the generation unit itself.